Aquarium filter



FIG. 1 is a perspective view of an aquarium filter showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is an exploded perspective view thereof. 

The ornamental design for an aquarium filter, as shown. 